A chronic total occlusion in a coronary artery, peripheral artery, vein, dialysis fistula, or other types of vasculature represents a challenge for percutaneous treatment. Percutaneous treatments are generally preferred revascularization options as compared to bypass surgery. Continuing improvements in equipment specifically developed for chronic total occlusions have allowed success rates to improve. Although the success rates for these types of procedures have improved, the procedures for percutaneous treatments still suffer from several drawbacks.
Patients without a successful percutaneous treatment may need to undergo bypass surgery or experience continuing symptoms from the occlusions.
A major obstacle within a chronic total occlusion may often be encountered while attempting to advance a catheter across the chronic total occlusion in a vasculature. A maximum resistance may be met at the most proximal point of the lesion, i.e. the firm, fibrous cap. While being advanced, a catheter may tend to deflect away from the fibrous cap towards the adventitial layer, often entering a false lumen. This off-axis displacement of the catheter often may result in a procedural failure.
Successful passage of the catheter may also be obstructed by randomly located calcified regions of atherosclerotic plaque within the mass of the lesion. Microchannels within the obstruction may be desirable targets for the tip of the catheter. However, these soft spots within the lesion are difficult to identify angiographically and are dispersed randomly within the matrix of the lesion.
Coronary arteries and other vasculatures tend to be non-linear conduits, often coursing over the surface of the epicardium and other tissues. The success of current technology is limited by this type of geometry. In current systems, a catheter or currently available catheter is advanced down a vasculature to the level of the obstruction. The catheter advancement may tend to proceed along the outer, greater curvature of the vasculature.
As a result, only a minor portion of the surface area of the obstruction may be encountered with sufficient force to allow passage of the catheter. On many occasions, the angle of encounter and/or the force applied to the fibrous cap may not be sufficient for crossing the fibrous cap with the catheter. If the tip of the catheter is curved prior to placement through the support catheter, direct longitudinal force may be compromised as the wire is advanced off axis. If a rapid exchange catheter system is used as catheter support, the catheter may buckle within the guide-catheter resulting in suboptimal longitudinal catheter force.
At times, a single lumen angioplasty balloon may be inflated just proximal to the chronic total occlusion in an attempt to center the catheter in the vessel lumen and provide additional support for the catheter. The angioplasty balloon, however, is occlusive to nearby vessels and exerts a significant outward force on the native vessel.
Approximately one-third of patients with coronary artery disease (CAD) and half of patients with peripheral artery disease (PAD), present with a chronic total occlusion (CTO) in the vessel. Despite overwhelming evidence of improved outcomes, attempted interventions remain low due to the lack of effective and convenient interventional tools. CTOs are characterized by fibrous caps with small micro-channels often in tortuous anatomy, leading to challenges for clinicians to gain guidewire access to treat the underlying disease.
In some situations, following an initial advancement of a first catheter to or through the cap of the occlusion, additional instruments or catheters may be subsequently advanced proximal to or through the occlusion. This may require removal of the first catheter and placement of a second catheter proximal to the occlusion. In placing the second catheter, the anatomy of the patient must be again be navigated, including the tortuous inner lumens of the heart, for example. However, the usual risks of the catheter being diverted off-course remain. Additionally, even if a guide wire is used, passage of the catheter through this anatomy can be traumatic for vessel walls.
Generally, needs exist for improved apparatus and methods for treating vasculatures.
More specifically, needs exist for improved apparatus and methods for efficiently and effectively passing a guidewire through a chronic total occlusion in a vasculature. In particular, there exists a need for improved apparatus and methods for efficiently and effectively passing a guidewire through a chronic total occlusion in a vasculature in such a way that the guidewire is reliably centered in the chronic total occlusion. Furthermore, there exists a need for improved apparatus and methods for navigating the vasculature in a way that is simple, reliable, and less traumatic to the vasculature.